Estimate With Compatible Numbers

Estimate with Compatible Numbers

Compatible numbers are numbers that are close to the originals but easier to work with mentally. They are chosen so the estimate is quick and reasonable.

1) Find numbers that are easy to use

Look for nearby numbers that divide evenly or are simple to compute with. The goal is not exactness, but convenience.

2) Keep the estimate reasonable

Choose replacements that stay close to the original values. If both numbers change, make sure the final estimate still makes sense compared with the exact problem.

3) Simplify the final answer

Carry out the easy calculation using the compatible numbers, then write the result as an estimate.

4) Check your estimate

Compare it to the original numbers. Ask:

• Is the answer close enough?
• Did I round in a way that makes the calculation easier?
• Does the estimate have the correct size?

Example strategy

If a problem is hard to compute exactly, replace one or both numbers with nearby values that work better together. Then do the simpler operation.

Good habit

After estimating, make sure your answer is labeled as an estimate and is simplified. That helps avoid confusing it with an exact answer.